<!DOCTYPE html>
<html>
<style>
.test {
  background-color: #fec;
  display: inline-block;
  width: 800px;
  height: 800px;
}

.second {
  box-shadow: inset 0 400px 1px 0px red;
}

.leftCut {
  position: absolute;
  margin-left: 0px;
  margin-top: 0px;
  width: 10px;
  height: 800px;
  background-color: black;
}

.rightCut {
  position: absolute;
  margin-left: 790px;
  margin-top: 0px;
  width: 10px;
  height: 800px;
  background-color: black;
}

.centerCut {
  position: absolute;
  margin-top: 395px;
  width: 800px;
  height: 20px;
  background-color: black;
}

</style>

<body>
<div class="leftCut"></div>
<div class="rightCut"></div>
<div class="centerCut"></div>
<div class="test second"></div>
</body>
</html>
